Field of the Invention
The present invention relates to an air separation device, as well as to an inerting device and an aircraft comprising such a device.
The invention relates more particularly to an air separation device comprising a casing with a generally cylindrical form which accommodates a filtration element comprising a bundle of hollow oblong fibers forming a membrane, the longitudinal axis of the fibers being parallel to the longitudinal axis of the cylindrical casing, the casing comprising at a first end an air inlet orifice, and, at a second end, a purified gas outlet orifice, the device comprising a unit for retention of fibers in the casing.
Related Art
The filtration of the gases from the air by means of a hollow fiber membrane is a process commonly used in industry, and in particular in the aeronautics field. This technology consists of collecting air obtained from a compressor/compressors or an engine/engines and making it circulate in a separation system containing a selective porous membrane which permits “passage” of only the molecules of one chemical type (oxygen for example). By compartmentalizing this system in a sealed manner, it is possible to recuperate at the outlet firstly oxygen-reduced air, which is therefore very rich in nitrogen, and secondly oxygen-enriched air. The nitrogen-enriched air can be used to inert fuel tanks for example, whereas the oxygen-enriched air can be simply discharged into the atmosphere.
The air separation systems generally comprise a casing comprising a metal cylinder (known as the envelope) closed at one end by a base (which is welded, glued or screwed on) and closed at the other end by a cover (which is generally screwed on or assembled by means of a flange). The cover is pierced by an inlet orifice which allows air to be admitted, whereas the base is pierced by an outlet orifice which permits collection of the nitrogen-enriched gas at the outlet of the system. Another outlet is provided for the separated gas (oxygen). The cylindrical envelope can for example be provided with an orifice which is perpendicular to the axis of the cylinder, thus permitting discharge of the oxygen filtered by the system.
The geometry of the inlet and outlet orifices can have different natures and shapes.
The filtration element which is disposed inside the casing is generally constituted by a bundle of hollow polymer fibers which are present in a very large number. The longitudinal axis of the fibers is aligned with the longitudinal axis of the cylinder of the casing.
At the ends of these fibers it is possible to provide a thermosetting material, ideally epoxy, which is cast and re-machined. These rigid material ends permit mechanical retention of the fibers, and cooperation with an O-ring seal(s) system in order to maintain the sealing between the different chambers of the system.
Document U.S. Pat. No. 7,717,983B2 describes a unit for axial retention of the bundle consisting of cones which are centered on both sides in hollow cylinders present on both sides of the outer faces of the membranes.
However, this arrangement generates rigidity of the assembly of the device, and gives rise to detrimental stresses in the membranes during certain operating phases of the system.